This invention relates to rail vehicle trucks and specifically to a lateral load absorbing assembly for mounting a bearing supported axle to a rail vehicle truck.
When a rail vehicle truck having a number of axles held parallel or in fixed relation to one another passes through a curve, the truck experiences "basic" lateral loading forces, known as curve negotiation forces which are related not to centrifugal force but, rather, the frictional forces between the rails and wheels. These forces would be present if the vehicle truck were stationary and the rails were moving beneath it with no driving or braking force, and these forces result from the fact that all wheels of the truck cannot line up tangent to the rails, especially with multiple axle trucks.
In addition to these "basic" lateral forces which occur with even theoretically perfect wheel and rail interaction, other dynamic lateral forces occur as a result of the inevitable imperfections and wear in the rails and wheels, and the wheels passing through switches and crossovers. These lateral forces are transmitted through the axle to the bearing and bearing housings supporting the axle on the truck.
The axles of a rail vehicle truck are rotatively supported parallel to one another in the truck frame by bearing assemblies which are mounted to the truck frame, generally within bearing housings which fit between members of the truck frame known as pedestals. The bearings themselves may be of the cylindrical roller type, in which case the axle end may move within the bearing housing laterally of the truck frame, while a thrust bearing located at the end of the bearing housing takes the lateral load of the end of the moving axle. In addition, a resilient element at the end of the bearing housing absorbs and cushions the lateral load induced thereon. Such a bearing mounting assembly is shown in the patent to Brittain U.S. Pat. No. 2,813,764. The bearing supporting the axle may also be of a tapered roller type, in which case the lateral motion just described is not feasible within the bearing housing itself, and the bearing housing instead will itself slide within the pedestal relative to the truck frame, with the axle rigid to the bearing and the bearing housing closely containing the bearing. Such a bearing mounting assembly is shown in the patent to Keller et al. U.S. Pat. No. 3,672,735. The structure shown there includes wear plates mounted between the truck frame and the bearing housing which are abraded under the frictional forces resulting from the sliding movement of the bearing housing, but includes no means for resiliently absorbing the thrust loads induced during curve negotiation.
It is known to provide rubber cushioning members internal to a tapered roller bearing housing. Janeway U.S. Pat. Nos. 2,267,466 and 2,335,120 each shows a composite metal and vulcanized rubber cushion assembly tightly bonded between a housing and a tapered bearing on a shaft. Because of the way the rubber assembly is bonded into the bearing housing, the rubber acts in vertical shear to absorb loads. It is obvious that a load absorbing assembly internal to a housing, besides being complex, is not easily removed and replaced. Such an assembly can also, of course, not be incorporated into a standard bearing housing without substantial modification to create the interior room necessary. These considerations are true for any bearing housing with an internal thrust absorption device.